He is from the planet Meteorus. His native race is one of the two sentient races of the planet. The other were the Moltens, a subterranean race. An episode had Meteor Man and his teamates resolving a conflict between two races.
His superpower is to selectively grow or shrink parts of his body. He gains superhuman strength in the limbs he grows and the strength necessary to wield a disproportionately large limb. He rarely shrinks to smaller sizes but does so for stealth purposes.